1. Field of the Invention
The present invention relates to a sealed screw operator for operating wedge drive screws or the like without breaching a hazardous material control border.
2. Related Art
Although the invention is not limited to such an application, the invention is particularly useful as applied to dual cask arrangements wherein an inner container or cask is installed inside of an outer shipping cask. In such arrangements, the inner container or cask is adapted to be removed from the shipping cask in instances where the exterior of the cask is contaminated with a hazardous material or materials. Loading and/or unloading operations may take place in a dry, non-hazardous environment and, under these circumstances, the inner container is not removed from the shipping cask. The inner cask includes a closure head which is secured by a series of wedge blocks operated by drive screws in the inner container walls. Because the inner container is not removed from the shipping cask, access to the drive screws during security of the closure head must be obtained through the wall of the shipping cask. It will be appreciated that, during operations, the goal is to avoid breaching boundaries contaminated with hazardous materials.
Patents of interest in this field include: U.S. Pat. No. 4,893,022 (Hall, et al.) which discloses an improved closure for covering and sealing a single cask radioactive waste system using sealing bolts. The sealing bolts are inserted through a bore having a shoulder to prevent the sealing bolts from inadvertently falling through the bore and breaking the seal. U.S. Pat. No. 4,456,827 (Botzem, et al.) discloses a transportation and storage container for radioactive wastes which are socketed screws in tapped sockets to seal the container from the admission of water. U.S. Pat. No. 4,636,645 (Kessinger) discloses a closure system for a storage cask for spent nuclear fuel which can be temporarily closed with a shear key and permanently closed via welding. U.S. Pat. No. 4,983,352 (Efferding) discloses a closure system for storing spent nuclear fuel. Studs are coated with sealant before screwing the studs into bores. U.S. Pat. No. 4,576,779 (McWilliams) discloses a wedge shaped member which is used to close the end of a transport flask and which advances a seal plate to close an opening in the base of the flask. U.S. Statutory Invention Registration No. HII (Basnar et al.) and U.S. Statutory Invention Registration No. HIO (Frank, et al.) both disclose a can-out hatch assembly. In both, an actuating shaft is inserted through a bore in a container for the purpose of positioning a hex head coupling against a pressure plate. The actuating shaft and the bore are provided with complimentary threads.
According to the invention, there is provided a sealed operator for operating (e.g., engaging and locking) a controllable element (e.g., a wedge screw drive such as disclosed above) in a dual container hazardous waste storage system.
In accordance with one aspect of the invention, there is provided, for use in a dual container hazardous waste containment system comprising an inner container, an outer container and an internal locking control element disposed inwardly of the outer container (such as the wedge screw drive element described above), a sealed operator device for operating the locking control element and adapted to be mounted in an aperture in the outer container, said operator comprising: a housing adapted to be sealingly mounted in said aperture, a bushing sealingly mounted within said housing for longitudinal movement with respect to said housing; a bearing assembly sealingly mounted within said bushing and comprising an outer bearing secured within said bushing and an inner bearing pivotably movable with respect to said outer bearing; and an operator element sealingly mounted within said inner bearing for movement therewith, said operator element including a stem portion secured within said inner bearing and a driving head adapted to engage the locking control element.
Preferably, the inner and outer bearings form a spherical bearing assembly. The bearings advantageously include respective polymer coated bearing surfaces.
In a preferred implementation, the outer bearing is a press fit within the bushing and the stem portion of the operator element is a press fit within the inner bearing. Advantageously, the outer surface of the housing is threaded for mounting in the aperture in the outer container.
In accordance with a further feature of importance, the bushing has an outer cylindrical surface including longitudinally extending guide track therein and the housing includes an inwardly extending guide pin received in the guide track for limiting angular movement of the bushing.
Preferably, at least one o-ring seal is provided between said bushing and said housing. More preferably, at least first and second o-rings are mounted in annular grooves in an outer cylindrical surface of the bushing.
In accordance with a further aspect of the invention a dual container hazardous waste containment system is provided which comprises an inner container, an outer container, a controllable element (e.g., the aforementioned wedge drive element) associated with the inner container and disposed inwardly of the outer container and a sealed operator device mounted in an aperture in the outer container for operating the controllable element, the sealed operator comprising: a housing sealingly mounted in the aperture; a bushing sealingly mounted within the housing for longitudinal movement with respect to the housing; a bearing assembly mounted within the bushing and comprising an outer bearing press fit within the bushing and an inner bearing pivotably movable with respect to the outer bearing; and an operator element mounted within the inner bearing for movement therewith, said operator element including a stem portion press fit within the inner bearing and a driving head adapted to engage the controllable element.
Further features and advantages of the present invention will be set forth in, or apparent from, the detailed description of preferred embodiments thereof which follows.